diff --git a/win32.c b/win32.c
index b5ab80cfbb..a7cee0e922 100644
--- a/win32.c
+++ b/win32.c
@@ -18,6 +18,7 @@
 #include <fcntl.h>
 #include "variables.h"
 #include "win32.h"
+#include <ctype.h>
 
 static bool _has_console;